public function undismiss_for_all( $slug ) {
		$user_query = new WP_User_Query( array(
			'meta_key'   => self::$meta_key,
			'meta_value' => $slug,
		) );

		$affected = 0;

		foreach ( $user_query->get_results() as $user ) {
			if ( $this->undismiss( $slug, $user->ID ) ) {
				$affected++;
			}
		}

		return $affected;
	}